1. Field of the Invention
Embodiments of the invention relate to a touch sensor integrated type display device.
2. Discussion of the Related Art
A touch sensor is installed in display devices such as a liquid crystal display, a field emission display, a plasma display panel, an electroluminescent display, and an electrophoresis display. The touch sensor is a kind of input device capable of inputting predetermined information when a user watching an image display device presses or touches a touch panel,.
The touch sensor used in the display devices may be classified into an add-on type touch sensor, an on-cell type touch sensor, and an integrated type (or in-cell type) touch sensor depending on its structure. The add-on type touch sensor is configured such that the display device and the add-on type touch sensor are individually manufactured and then the add-on type touch sensor is attached to an upper substrate of the display device. The on-cell type touch sensor is configured such that components constituting the on-cell type touch sensor are directly formed on the surface of an upper glass substrate of the display device. The in-cell type touch sensor is configured such that the in-cell type touch sensor is mounted inside the display device to thereby achieve thin profile of the display device and to increase the durability of the display device.
However, because the add-on type touch sensor has the structure in which the completed add-on type touch sensor is mounted on the display device, a thickness of the display device increases. Further, the visibility of the display device is reduced because of a reduction in a brightness of the display device. Because the on-cell type touch sensor has the structure in which the on-cell type touch sensor is formed on the surface of the glass substrate of the display device, the on-cell type touch sensor shares the glass substrate with the display device. Therefore, a thickness of the display device using the on-cell type touch sensor is less than a thickness of the display device using the add-on type touch sensor. However, the entire thickness of the display device using the on-cell type touch sensor increases because of a touch driving electrode layer, a touch sensing electrode layer, and an insulating layer for insulating the touch driving electrode layer and the touch sensing electrode layer, which constitute the on-cell type touch sensor. Further, the number of processes and the manufacturing cost in the on-cell type touch sensor increase.
The in-cell type touch sensor can solve the problems generated in the add-on type touch sensor and the on-cell type touch sensor because of the advantages of the thin profile and the durability improvement. Examples of the in-cell type touch sensor include a light type touch sensor, a capacitive type touch sensor, etc.
In the light type touch sensor, a light sensing layer is formed on a thin film transistor (TFT) array substrate of the display device, and it is possible to recognize light reflected by an object existing in a touched portion using light or infrared light from a backlight unit. The light type touch sensor shows a relatively stable driving performance in dark surroundings, but light stronger than the reflected light acts as a noise in bright surroundings. The light type touch sensor may erroneously recognize a non-touch operation as an touch operation even surroundings are slightly bright because an intensity of light reflected by the actual touch operation is very weak. In particular, the light type touch sensor may not recognize the touch operation because an intensity of light in the surroundings exposed to solar light is very strong.
Examples of the capacitive type touch sensor include a self capacitive type touch sensor and a mutual capacitive type touch sensor. The mutual capacitive type touch sensor divides a common electrode of a display device into touch driving electrode regions and touch sensing electrode regions to form mutual capacitances between the touch driving electrode regions and the touch sensing electrode regions. Hence, the mutual capacitive type touch sensor measures changes in the mutual capacitances generated in a touch operation, thereby recognizing the touch operation.
In the mutual capacitive type touch sensor, a common electrode is divided into a plurality of touch cells formed on the same layer, and each of the touch cells is divided into a touch driving electrode and a touch sensing electrode. As mentioned above, because the touch driving electrodes and the touch sensing electrodes are formed on the same layer, touch driving lines for connecting the touch driving electrodes and touch sensing lines for connecting the touch sensing electrodes are necessary so that the touch driving electrodes do not contact the touch sensing electrodes. For this, in the related art, the touch driving lines were formed of the same metal as gate lines when the gate lines of the display device were formed, thereby connecting the touch driving electrodes to one another in a x-axis direction. Further, the touch sensing lines were formed of metal formed on a layer different from the formation layer of the touch driving lines, the touch driving electrodes, and the touch sensing electrodes, thereby connecting the touch sensing electrodes to one another in a y-axis direction.
However, when the touch driving lines and the touch sensing lines were formed on the different layers, the design of a TFT array was complicated, and a bezel width of the display device increased because of the left-right line design of the touch driving lines.
Accordingly, the need of a touch sensor integrated type display device capable of solving the problems of the above-described kinds of touch sensors was on the rise.